Abstract

Thin films of superconducting Y1Ba2Cu3O7 have been used as the active element in an optically triggered fast opening switch. Both granular and highly c-axis oriented films, ranging in thickness from 2000 Å to 7000 Å, were subject to 150 psec pulses from a Nd:YAG laser and exhibited switching from the superconducting to the normal state in times ranging from 1 nsec to 10 nsec, followed by a much slower decay over 100 nsec to 1 µsec. The magnitude of the voltage response and the slow decay can be explained in terms of a simple bolometric effect, while the rapid switching of even the thicker films is indicative of nonequilibrium hot electron transport from the absorbing surface layer to the remaining film thickness. At higher temperatures the response time is slower than 10 nsec, indicating a more diffusive behavior to the electron heat transport. These results give some indication of the electron-phonon collision time and help set limits to the maximum film thickness useable for laser triggered fast opening switches.